"WikiLeaks changed its hosting two times in the last 12 hours," said Hypponen in an interview Monday. "[WikiLeaks] changed from the French host that it's used for some time to Amazon's cloud ... and one of those IP adresses is in the U.S."

Traces of WikiLeaks.org by Computerworld showed that WikiLeaks' URL resolved to at least two Amazon-owned addresses, one in Ireland and the other in Seattle, Wash.

According to Hypponen, a hacker who goes by the nickname "The Jester" -- in leetspeak, it's "th3j35t3r" -- has claimed responsibility for the attacks against WikiLeaks. In several Twitter messages, Jester said he launched the attacks "for [WikiLeaks] attempting to endanger the lives of our troops, 'other assets' & foreign relations."

Jester is a likely candidate, said Hypponen. "He took responsibility, and more importantly, he has demonstrated the capability. He also seems to have a motive."

The hacker, who Hypponen believes is in Russia based on his Hotmail e-mail address, has boasted before of denial of service attacks against Islamic jihadist Web sites.

In a July 2010 interview with the U.K.-bassed Ethical Hack3r site, Jester has claimed he is "ex-mil," or ex-military, and said his self-set mission is "to cause disruption to the online efforts of jihadists on the Internet."

Amazon did not immediately reply for a request for comment about its servers hosting WikiLeaks.

Earlier this year, U.S. authorities criticized WikiLeaks for releasing a cache of military documents relating to the U.S. wars in Afghanistan and Iraq.

Today, U.S. Secretary of State Hillary Rodham Clinton condemned WikiLeaks for releasing the diplomatic cables.

"The United States strongly condemns the illegal disclosure of classified information," Clinton said in a Monday news conference. "It puts people's lives in danger, threatens our national security, and undermines our efforts to work with other countries to solve shared problems."

She also implicitly threatened WikiLeaks. "I want you to know that we are taking aggressive steps to hold responsible those who stole this information," she said. "I have directed that specific actions be taken at the State Department, in addition to new security safeguards at the Department of Defense and elsewhere to protect State Department information so that this kind of breach cannot and does not ever happen again."